1. Field of the Invention
This invention relates generally to water purification systems and more particularly to a water purification accomplished by introduction of molecular iodine into the water supply to impart a desired iodine residual by use of an iodinated exchange resin bed which is recharged periodically during use.
2. Brief Description of the Prior Art
The use of chlorine for water purification is well known. Iodine has also been used for the same purpose.
In space activities, i.e., space shuttle, orbiter lab, Lunar base, Mars base, deep space missions, etc., continuous, long-term microbial control in the water supply for potable, hygiene, and experimental water has been accomplished by introduction of molecular iodine into the water supply to impart a desired iodine residual. The water is passed through an iodinated anion exchange resin bed which releases molecular iodine.
Lambert and Fina U.S. Pat. Nos. 3,817,860 and 3,923,366 disclose methods of disinfecting water and demand bacteriacides but do not show in situ regeneration.
Barnes U.S. Pat. No. 4,888,118 discloses a water purification process in which the water is passed through a mass of nylon 4 complexed with iodine. The treated water is subsequently passed through nylon 4 to remove iodine from the water. The nylon 4 used in both treatment zones can be in any form, preferably a form having a high surface area, e.g., powder, fiber, drawn or undrawn, staple fiber, knitted or non-woven fabrics or pulp fibrils.
Keblys et al U.S. Pat. No. 4,131,645 discloses an iodine recovery process by repeated cycles of passing an iodine-containing brine through a basic ion exchanger to absorb iodine and then oxidizing adsorbed iodide to iodine by passing an acidified aqueous iodate solution through the exchange resin.
Abrams U.S. Pat. No. 4,849,111 discloses a method and apparatus for regenerating a dynamic adsorber system which removes a contaminant from a fluid. The bed is periodically cleansed by flowing a clean fluid therethrough.
The present invention is distinguished over the prior art in general, and these patents in particular by a method and apparatus disclosed for maintaining continuous, long-term microbial control in the water supply for potable, hygiene, and experimental water for space activities, i.e., space shuttle, orbiter lab, Lunar base, Mars base, deep space missions, etc., as well as various terrestrial applications. The water purification is accomplished by introduction of molecular iodine into the water supply to impart a desired iodine residual. The water is passed through an iodinated anion exchange resin bed. The iodine is bound as I.sub.n.sup.-, where n is an odd integer greater than three, at the anion exchange sites and releases I.sub.2 into the water stream flowing through the bed. Suitable resins are strong base anion exchange resins such as AMBERLITE IRA 401S (Rohm & Haas); DOWEX SBR (Dow Chemical); and IONAC ASB-1P (Sybron Corp.). The concentration of I.sub.2 in the flowing water gradually decreases and the ion-exchange bed has had to be replaced. In a preferred embodiment, a bed of iodine crystals is provided with connections for flowing water therethrough to produce a concentrated (substantially saturated) aqueous iodine solution which is passed through the iodinated resin bed to recharge the bed with bound iodine. The iodinated resin bed has been recharged up to eight times during continuous use to permit an extended life to the system. The bed of iodine crystals is connected in parallel with the iodinated resin bed and is activated periodically, e.g., by timer, by measured flow of water, or by iodine residual level, to recharge the bed.